first re-commit.

pigpio-master/EXAMPLES/CPP/ROTARY_ENCODER/README

@@ -0,0 +1,4 @@
+Class to decode a mechanical rotary encoder.
+
+Follow the instructions in the test file to build and run.
+

pigpio-master/EXAMPLES/CPP/ROTARY_ENCODER/rotary_encoder.cpp

@@ -0,0 +1,84 @@
+#include <iostream>
+
+#include <pigpio.h>
+
+#include "rotary_encoder.hpp"
+
+/*
+
+             +---------+         +---------+      0
+             |         |         |         |
+   A         |         |         |         |
+             |         |         |         |
+   +---------+         +---------+         +----- 1
+
+       +---------+         +---------+            0
+       |         |         |         |
+   B   |         |         |         |
+       |         |         |         |
+   ----+         +---------+         +---------+  1
+
+*/
+
+void re_decoder::_pulse(int gpio, int level, uint32_t tick)
+{
+   if (gpio == mygpioA) levA = level; else levB = level;
+
+   if (gpio != lastGpio) /* debounce */
+   {
+      lastGpio = gpio;
+
+      if ((gpio == mygpioA) && (level == 1))
+      {
+         if (levB) (mycallback)(1);
+      }
+      else if ((gpio == mygpioB) && (level == 1))
+      {
+         if (levA) (mycallback)(-1);
+      }
+   }
+}
+
+void re_decoder::_pulseEx(int gpio, int level, uint32_t tick, void *user)
+{
+   /*
+      Need a static callback to link with C.
+   */
+
+   re_decoder *mySelf = (re_decoder *) user;
+
+   mySelf->_pulse(gpio, level, tick); /* Call the instance callback. */
+}
+
+re_decoder::re_decoder(int gpioA, int gpioB, re_decoderCB_t callback)
+{
+   mygpioA = gpioA;
+   mygpioB = gpioB;
+
+   mycallback = callback;
+
+   levA=0;
+   levB=0;
+
+   lastGpio = -1;
+
+   gpioSetMode(gpioA, PI_INPUT);
+   gpioSetMode(gpioB, PI_INPUT);
+
+   /* pull up is needed as encoder common is grounded */
+
+   gpioSetPullUpDown(gpioA, PI_PUD_UP);
+   gpioSetPullUpDown(gpioB, PI_PUD_UP);
+
+   /* monitor encoder level changes */
+
+   gpioSetAlertFuncEx(gpioA, _pulseEx, this);
+   gpioSetAlertFuncEx(gpioB, _pulseEx, this);
+}
+
+void re_decoder::re_cancel(void)
+{
+   gpioSetAlertFuncEx(mygpioA, 0, this);
+   gpioSetAlertFuncEx(mygpioB, 0, this);
+}
+

pigpio-master/EXAMPLES/CPP/ROTARY_ENCODER/rotary_encoder.hpp

@@ -0,0 +1,35 @@
+#ifndef ROTARY_ENCODER_HPP
+#define ROTARY_ENCODER_HPP
+
+#include <stdint.h>
+
+typedef void (*re_decoderCB_t)(int);
+
+class re_decoder
+{
+   int mygpioA, mygpioB, levA, levB, lastGpio;
+
+   re_decoderCB_t mycallback;
+
+   void _pulse(int gpio, int level, uint32_t tick);
+
+   /* Need a static callback to link with C. */
+   static void _pulseEx(int gpio, int level, uint32_t tick, void *user);
+
+
+   public:
+
+   re_decoder(int gpioA, int gpioB, re_decoderCB_t callback);
+   /*
+      This function establishes a rotary encoder on gpioA and gpioB.
+
+      When the encoder is turned the callback function is called.
+   */
+
+   void re_cancel(void);
+   /*
+      This function releases the resources used by the decoder.
+   */
+};
+
+#endif

pigpio-master/EXAMPLES/CPP/ROTARY_ENCODER/test_rotary_encoder.cpp

@@ -0,0 +1,45 @@
+#include <iostream>
+
+#include <pigpio.h>
+
+#include "rotary_encoder.hpp"
+
+/*
+
+REQUIRES
+
+A rotary encoder contacts A and B connected to separate gpios and
+the common contact connected to Pi ground.
+
+TO BUILD
+
+g++ -o rot_enc_cpp test_rotary_encoder.cpp rotary_encoder.cpp -lpigpio -lrt
+
+TO RUN
+
+sudo ./rot_enc_cpp
+
+*/
+
+void callback(int way)
+{
+   static int pos = 0;
+
+   pos += way;
+
+   std::cout << "pos=" << pos << std::endl;
+}
+
+int main(int argc, char *argv[])
+{
+   if (gpioInitialise() < 0) return 1;
+
+   re_decoder dec(7, 8, callback);
+
+   sleep(3000);
+
+   dec.re_cancel();
+
+   gpioTerminate();
+}
+